


public class Solution {
    public class ListNode {
    int val;
    ListNode next = null;

    ListNode(int val) {
        this.val = val;
    }
}
    public ListNode deleteDuplication(ListNode pHead) {
        if(pHead==null){
            return null;
        }
        ListNode res=new ListNode(0);
        res.next=pHead;
        ListNode p=res;
        while(p.next!=null&&p.next.next!=null){
            if(p.next.val==p.next.next.val){
                int tmp=p.next.val;
                while(p.next!=null&&p.next.val==tmp){
                    p.next=p.next.next;
                }
            }else{
                p=p.next;
            }
        }
        return res.next;
    }
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        if (l1 == null) {
            return l2;
        } else if (l2 == null) {
            return l1;
        } else if (l1.val < l2.val) {
            l1.next = mergeTwoLists(l1.next, l2);
            return l1;
        } else {
            l2.next = mergeTwoLists(l1, l2.next);
            return l2;
        }
    }
}